The present invention is generally directed to toner processes, and more specifically, to chemical processes which involve the aggregation and fusion of latex, colorant, like pigment and additive particles into toner particles, and wherein aggregation can be controlled by adjusting, or decreasing the pH which is in the range of 4.5 to 6, to about 2 to 4 of the mixture of latex and colorant dispersion by the addition of an acid, and wherein there is selected a latex comprised of for example, submicron resin particles in the size range of 0.1 to 0.4 microns in volume average diameter, suspended in an aqueous phase of water, nonionic and anionic surfactants to which a colorant dispersion comprising for example, submicron colorant particles in the size range of 0.08 to 0.3 microns in volume average diameter, cationic surfactant, and a hydrodispersed polymer wherein the hydrodispersed polymer refers to a polymer resin containing a large number of acid groups in the range of for example, about 20 to about 300, and more specifically from about 30 to about 250 of acid groups and which resin can be dispersed or solubilized in an aqueous media, which media is in a pH range of about 7 to about 12. The acid groups can be comprised of acrylic acid, maleic acid, methacrylic acid, itaconic acid and the like, and which acids are incorporated into the backbone of the polymer chain during the polymerization process, and more specifically the acid groups are for example, JohncrylTM available from S.C Johnson & Son, UnicidTM from Petrolite, acrylate--acrylic and styrene butadiene emulsions from Dow Chemicals and which are generally considered styrene acrylic polymers.
The toners generated with the processes of the present invention can be selected for known electrophotographic imaging and printing processes, including digital processes.
In xerographic systems, especially color systems, small sized toners of preferably from about 2 to about 7 microns are important to the achievement of high image quality for process color applications. It is also important to have a low image pile height to eliminate, or minimize image feel and avoid paper curling after fusing. Paper curling can be particularly pronounced in xerographic color processes primarily because of the presence of relatively high toner coverage as a result of the application of three to four color toners. During the fusing step, moisture escapes from the paper due to high fusing temperatures of from about 120.degree. C. to 200.degree. C. In the situation wherein with only one layer of toner is selected, such as in one-color black or highlight color xerographic applications, the amount of moisture driven off during fusing can be reabsorbed by the paper and the resulting print remains relatively flat with minimal paper curl. In process color where toner coverage is high, the relatively thick toner plastic covering on the paper can inhibit the paper from reabsorbing the moisture, and cause substantial paper curling. These and other imaging shortfalls and problems are avoided or minimized with the toners and processes of the present invention.
Also, it is preferable to select a toner particle sizes, such as from about 2 to about 7 microns, and with a high colorant, especially pigment loading such as from about 4 to about 15 percent by weight of toner, so that the mass of toner necessary for attaining the required optical density and color gamut can be significantly reduced to eliminate or minimize paper curl. Lower toner mass also ensures the achievement of image uniformity. However, higher pigment loadings often adversely affect the charging behavior of toners. For example, the charge levels may be too low for proper toner development or the charge distributions may be too wide and toners of wrong charge polarity may be present. Furthermore, higher pigment loadings may also result in the sensitivity of charging behavior to charges in environmental conditions such as temperature and humidity. Toners prepared in accordance with the processes of the present invention minimize, or avoid these disadvantages.